1. Field of the Invention
The present invention relates generally to the field of magnetic disk drives, and more particularly to an adjustable suspension for fine tuning a clearance between a read/write head and a magnetic disk.
2. Description of the Prior Art
Magnetic disk drives are used to store and retrieve data for digital electronic apparatuses such as computers. In FIGS. 1 and 2, a magnetic disk data storage system 10 includes an enclosure 12 (shown in cross-section), a disk drive motor 14, and a magnetic disk, or media, 16 supported for rotation by a drive spindle 17 of motor 14. Also included are an actuator 18 and an arm 20 attached to an actuator spindle 21 of actuator 18. A suspension 22 is coupled at one end to the arm 20 and at another end to a read/write head 24. The suspension 22 and the read/write head 24 are commonly collectively referred to as a head gimbal assembly (HGA). The read/write head 24 typically includes an inductive write element and a magnetoresistive read element that are held in a very close proximity to the magnetic disk 16. As the motor 14 rotates the magnetic disk 16, as indicated by the arrow R, an air bearing is formed under the read/write head 24 causing the read/write head 24 to lift slightly off of the surface of the magnetic disk 16, or, as it is commonly termed in the art, to “fly” above the magnetic disk 16. Data bits can be written or read along a magnetic “track” of the magnetic disk 16 as the magnetic disk 16 rotates past the read/write head 24. The actuator 18 moves the read/write head 24 from one magnetic track to another by pivoting the arm 20 and the suspension 22 in an arc indicated by arrows P. The design of magnetic disk data storage system 10 is well known to those skilled in the art.
The magnetic disk data storage industry has been very successful at achieving ever greater data densities on magnetic disks 16 by pursuing the miniaturization of various components such as the read/write head 24. In particular, the miniaturization of the read/write head 24, in combination with advances in their designs and the surfaces of magnetic disks 16, has supported ever increasing data densities by allowing the read/write head 24 to fly ever closer to the surface of the magnetic disk 16. Lower fly heights are advantageous because the decreased spacing between the read/write head 24 and the magnetic disk 16 allows for a size of the data bits written to the magnetic disk 16 to be reduced, and for such smaller data bits to be sensed by the read element of the read/write head 24. Unfortunately, lower fly heights also increase the likelihood that the flying read/write head 24 will collide catastrophically (“crash”) with the magnetic disk 16.
Moreover, the read/write head 24 does not maintain the same fly height under all circumstances. For example, the fly height varies as a function of the position over the magnetic disk 16, in other words, the fly height for the read/write head 24 is different when positioned over the inside diameter (ID), center, and outside diameter (OD) of the magnetic disk 16. Likewise, changes in air pressure due to changes in temperature or elevation will also effect the fly height. Accordingly, what were once minor variations in fly height become significant variations as the spacing between the read/write head 24 and the magnetic disk 16 is further decreased.
Therefore, what is needed is a mechanism for actively adjusting the fly height of a read/write-head to maintain a more uniform spacing between the read/write head and a disk.